1. Field of the Invention
The present invention relates to an optical communication module using a refraction plate for optical axis compensation, and its manufacturing method.
2. Description of the Related Art
In recent years, multi-functionalization of an optical module aimed at space saving has been advancing. Along with it, the necessity of integrating a plurality of optical components into one optical module arises. However, the optical axial alignment tolerance in the case of optical coupling and fixation of optical components is extremely narrow, because the spot size is small (nearly 1 to several μm).
Often, when a plurality of optical components is fixed for being coupled optically, a positional misalignment can arise at the time of the fixation. When the positional misalignment arises, optical loss increases, and then, many characteristics of the optical module which is constructed of the coupled optical components deteriorate. In the prior art, as shown in the Japanese Patent Laid-Open No. 2004-272143, there is a method of optical axis compensation by inserting a parallel plate in a focal point side of a dual lens system.
In addition, the Japanese Patent Laid-Open No. 2003-248144, shows an optical transmission module in which a semiconductor laser diode and an optical fiber are optically coupled through a lens. And a positional misalignment compensation window is provided between a lens and an optical fiber, wherein the positional misalignment compensation window consists of a material whose refractive index varies widely with temperature, and is constructed into a parallel plate, a wedge prism, or the like.
However, as shown in the Japanese Patent Laid-Open No. 2004-272143, in the method of optical axis compensation by inserting a parallel plate in a focal point side of a dual lens system, because the focal length of a lens for a dual lens system is generally short, a space for inserting the parallel plate is limited. Therefore, integration of an optical module is difficult.
In addition, as shown in the Japanese Patent Laid-Open No. 2003-248144, in the case that a parallel plate for optical axis adjustment is made of a silicone-based resin, an epoxy system resin, polyimide, or the like where the refractive indices of the main components varies widely with temperature change, the amount of misalignment of an optical axis is different in every optical transmission module. Therefore, the usage of the module is difficult.